A carbon fiber-reinforced composite material which is comprised of carbon fiber and a matrix resin is light in weight and excellent in dynamic characteristics, so is being used for golf clubs, tennis rackets, fishing rods, and other sporting goods and also structural materials for aircraft, vehicles, etc., reinforcement of concrete structures, and other broad fields. Further, carbon fiber has conductivity, so the carbon fiber-reinforced composite material exhibits excellent electromagnetic shielding ability. It is being used for housings of notebook computers, video cameras, and other electrical and electronic equipment and is helpful in reducing the thickness of housings and lightening the weight of equipment.
As such a carbon fiber-reinforced composite material, for example, Patent Document 1 describes carbon fiber coated with a specific sizing agent having a vinylidene group and epoxy group, which is excellent in resin impregnation by an unsaturated polyester resin, vinyl ester resin, acryl resin, or other radical polymerized resin, which is further excellent in bond strength between these resins and carbon fiber, and which further gives a stable effect of improvement of physical properties, sheets of such carbon fiber, and a carbon fiber-reinforced resin composition which uses that carbon fiber as a reinforcing material. Patent Document 2 describes a carbon fiber-reinforced sheet shaped material containing unsaturated polyester as the main ingredient of the matrix resin, which has a smooth surface, and which is excellent in coatability. This literature describes that if mixing into a resin composition used for preparing the material, a polyisocyanate compound or a mixture of a polyisocyanate compound and a monoisocyanate compound, the impregnability of the resin composition into the carbon fiber is improved.
Further, Patent Document 3 describes a thermoplastic resin obtained by impregnating a polymerizable composition containing a norbornene-based monomer, metathesis polymerization catalyst, chain transfer agent, and cross-linking agent into a fiber material, then performing bulk polymerization and describes a cross-linked resin obtained by cross-linking that resin. As an example of the fiber material, carbon fiber is described.
In this regard, Patent Document 4 describes, relating to the carbon fiber-reinforced composite material such as described in Patent Document 3, that if a sizing agent is deposited on the carbon fiber, the polymerization of the norbornene-based monomer is blocked and there is a detrimental effect on the physical properties of the obtained thermoplastic resin and cross-linked resin and that, furthermore, a polymer comprised of a generally low polarity norbornene-based monomer bonds with the carbon fiber by the anchor effect, so it is preferable that there be no extra intermediate layer made of a sizing agent between the carbon fiber and that polymer as a matrix resin.